Light-emitting device having a patterned surface

ABSTRACT

A light-emitting device comprises a substrate having a top surface and a plurality of patterned units protruding from the top surface; and a light-emitting stack formed on the substrate and having an active layer with a first surface substantially parallel to the top surface, wherein one of the plurality of patterned units comprises a plurality of connecting sides constituting a polygon shape in a top view of the light-emitting device, the one of the plurality of patterned units comprises a vertex and a plurality of inclined surfaces respectively extending from the plurality of connecting sides, the plurality of inclined surfaces commonly join at the vertex in a cross-sectional view of the light-emitting device, the vertex being between the top surface of the substrate and the first surface of the active layer, and six of the plurality of patterned units forms a hexagon in the top view of the light-emitting device.

RELATED APPLICATION

This application is a continuation application of U.S. patentapplication Ser. No. 14/997,258, entitled “A LIGHT-EMITTING DEVICEHAVING A PATTERNED SURFACE”, filed on Jan. 15, 2016, which is acontinuation application of U.S. patent application Ser. No. 14/132,819,entitled “A LIGHT-EMITTING DEVICE HAVING A PATTERNED SURFACE”, filed onDec. 18, 2013, which is a continuation application of U.S. patentapplication Ser. No. 12/646,553, entitled “A LIGHT-EMITTING DEVICEHAVING A PATTERNED SURFACE”, filed on Dec. 23, 2009, which is acontinuation-in-part of U.S. patent application Ser. No. 12/222,548,entitled “Stamp Having Nanoscale Structure And Applications Thereof InLight-Emitting Device”, filed on Aug. 12, 2008 claiming the right ofpriority based on TW application Ser. No. 097150633 filed on Dec. 24,2008; the contents of which are incorporated herein by reference intheir entireties.

BACKGROUND

1. Technical Field

The present disclosure relates to a light-emitting device having apatterned surface.

2. Description of the Related Art

Recently, efforts have been devoted to promote the luminance of thelight-emitting diode (LED) in order to implement the device in thelighting domain, and further procure the goal of energy conservation andcarbon reduction. There are two major aspects to promote luminance. Oneis to increase the internal quantum efficiency (IQE) by improving theepitaxy quality to enhance the combination efficiency of electrons andholes. The other is to increase the light extraction efficiency (LEE)that emphasizes on the light which is emitted by the light-emittinglayer capable of escaping outside the device, and therefore reducing thelight absorbed by the LED structure.

Surface roughening technology is one of the efficient methods to enhanceluminance. FIG. 7 shows a known LED 700 having a patterned substrate.LED 700 comprises a growth substrate 701, an epitaxial stack, a firstelectrode 707, and a second electrode 708. The surface 701 a of thegrowth substrate 701 has a plurality of trapezoid depression forimproving the light-extraction efficiency. The epitaxial stack comprisesa buffer layer 702 grown on the growth substrate, a non-dopedsemiconductor layer 703 grown on the buffer layer 702, a firstsemiconductor layer 704 with first conductivity-type grown on thenon-doped semiconductor layer 703, an active layer 705 grown on thefirst semiconductor layer 704, a second semiconductor layer 706 withsecond conductivity-type grown on the active layer 705. The firstelectrode 707 is formed on the exposed first semiconductor layer 704,and the second electrode 708 is formed on the second semiconductor layer706.

The ratio of the pattern width to the width between patterns of thesubstrate surface 701 a is generally designed to be around 1. Therefore,a considerable portion of the substrate surface 701 a is still parallelto the surface of the active layer 705 a, and the light emitted from theactive layer 705 to the parallel substrate surface is easily reflectedback to the epitaxial stack because of total internal reflection (TIR)effect and absorbed by the epitaxial stack to generate heat. It worsensboth the light extraction efficiency and the heat dissipation problems.Nevertheless, the pattern is usually formed deeper in order tocompensate the light loss due to the parallel (unpatterned) region, butthe high aspect ratio of the deeper pattern causes difficulty forsubsequently epitaxial growth and adversely affects the epitaxialquality.

Another prior technique for roughen surface is to utilize mechanicallypolishing method to form a randomly distributed rough patterns on thesubstrate surface. By this method, it is hard to control the rougheneddimension, such as the depth or the width. Moreover, the epitaxialquality is not good by growing an epitaxial layer on the randomly roughsurface.

SUMMARY OF THE DISCLOSURE

The disclosure provides a light-emitting device. The light-emittingdevice comprises: a substrate having a first patterned unit; and alight-emitting stack on the substrate and having an active layer with afirst surface; wherein the first patterned unit, protruding in adirection from the substrate to the light-emitting stack, has sidesurfaces abutting with each other and substantially non-parallel to thefirst surface in cross-sectional view, and has a non-polygon shape intop view.

A light-emitting device includes a substrate having a top surface and afirst patterned unit bulged on the top surface; and a light-emittingstack formed on the substrate and having an active layer with a firstsurface substantially parallel to the top surface; wherein a base of thefirst patterned unit has a non-polygon shape in a top view, and in across-sectional view: the first patterned unit has a vertex, a firstinclined line segment, and a second inclined line segment, and the firstinclined line segment and the second inclined line segment connect atthe vertex.

A light-emitting device includes a substrate having a top surface and afirst patterned unit bulged on the top surface; and a light-emittingstack formed on the substrate and having an active layer with a firstsurface substantially parallel to the top surface, wherein the firstpatterned unit has a non-polygon shape in a top view, and a firstinclined line and a second inclined line directly connect to the topsurface to form a vertex in a cross-sectional view, and wherein thefirst patterned unit is substantially formed in a V-shape in thecross-sectional view.

A light-emitting device includes a substrate having a top surface and aplurality of first patterned units bulged on the top surface; and alight-emitting stack formed on the substrate and having an active layerwith a first surface substantially parallel to the top surface, whereineach of the plurality of first patterned units has a non-polygon shapein a top view, and a first inclined line and a second inclined linedirectly connect to the top surface to form a vertex in across-sectional view, and wherein each of the plurality of firstpatterned units is substantially formed in a V-shape in thecross-sectional view.

A light-emitting device comprises a substrate having a top surface and aplurality of patterned units protruding from the top surface; and alight-emitting stack formed on the substrate and having an active layerwith a first surface substantially parallel to the top surface; whereinone of the plurality of patterned units has a vertex, a first inclinedsurface, and a second inclined surface, and the first inclined surfaceand the second inclined surface commonly join at the vertex from across-sectional view of the light-emitting device.

A light-emitting device comprises a substrate having a top surface and aplurality of patterned units protruding from the top surface; and alight-emitting stack formed on the substrate and having an active layerwith a first surface substantially parallel to the top surface, whereinone of the plurality of patterned units comprises a plurality ofconnecting sides constituting a polygon shape in a top view of thelight-emitting device, the one of the plurality of patterned unitscomprises a vertex and a plurality of inclined surfaces respectivelyextending from the plurality of connecting sides, the plurality ofinclined surfaces commonly join at the vertex in a cross-sectional viewof the light-emitting device, the vertex being between the top surfaceof the substrate and the first surface of the active layer, and six ofthe plurality of patterned units forms a hexagon in the top view of thelight-emitting device.

A light-emitting device comprises a substrate having a top surface and aplurality of patterned units protruding from the top surface; and alight-emitting stack formed on the substrate and having an active layerwith a first surface substantially parallel to the top surface, whereinone of the plurality of patterned units comprises a plurality ofconnecting sides constituting a polygon shape in a top view of thelight-emitting device, the one of the plurality of patterned unitscomprises a vertex and a plurality of inclined surfaces respectivelyextending from the plurality of connecting sides, the plurality ofinclined surfaces commonly joining at the vertex and the plurality ofinclined surfaces comprising a triangular shape, and multiple of theplurality of patterned units form a polygon surrounding another one ofthe plurality of patterned units in the top view of the light-emittingdevice.

A light-emitting device comprises a substrate having a top surface and aplurality of patterned units protruding from the top surface; and alight-emitting stack formed on the substrate and having an active layerwith a first surface substantially parallel to the top surface, whereinone of the plurality of patterned units comprises a first inclined lineand a second inclined line protruding from the top surface of thesubstrate, the first inclined line and the second inclined line forminga vertex in a cross-sectional view of the light-emitting device, the oneof the plurality of patterned units comprises a non-polygon shape in atop view of the light-emitting device, three of the plurality ofpatterned units forms a triangle in the top view of the light-emittingdevice.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a light-emitting device in accordance with the firstembodiment of the present disclosure.

FIG. 2 shows a light-emitting device in accordance with the secondembodiment of the present disclosure.

FIGS. 3A and 3B show a light-emitting device in accordance with thethird embodiment of the present disclosure.

FIG. 4 shows a light-emitting device in accordance with the fourthembodiment of the present disclosure.

FIG. 5 shows a light-emitting device in accordance with the fifthembodiment of the present disclosure.

FIG. 6A to 6E show embodiments of the top views of the patterned surfacein accordance with the present disclosure.

FIG. 7 shows a known structure of a light-emitting diode.

DETAILED DESCRIPTION OF THE EMBODIMENTS

FIG. 1 shows a light-emitting device 100 in accordance with a firstembodiment of the present disclosure. The light-emitting device 100comprises a growth substrate 101, an intermediate layer comprising abuffer layer 102 and/or an undoped semiconductor layer 103 epitaxiallygrown on the growth substrate 101, a first contact layer 104 with firstconductivity-type epitaxially grown on the intermediate layer, a firstcladding layer 105 with first conductivity-type epitaxially grown on thefirst contact layer 104, an active layer 106 epitaxially grown on thefirst cladding layer 105, a second cladding layer 107 with secondconductivity-type epitaxially grown on the active layer 106, a secondcontact layer 108 with second conductivity-type epitaxially grown on thesecond cladding layer 107, a current spreading layer 109 formed on thesecond contact layer 108 and forming an ohmic contact with the secondcontact layer 108, a first electrode 110 formed on the exposed firstcontact layer 104 by evaporation or sputtering method, and a secondelectrode 111 formed on the current spreading layer 109 by evaporationor sputtering method; wherein the growth substrate 101 has a patternedsurface 101 a comprising a plurality of ordered pattern units, and eachof the plurality of ordered pattern units is compactly disposed, forexample, at least one of the plurality of pattern units is substantiallycontacted with the neighboring units. According to the embodiment, anyregion of the patterned surface 101 a, e.g. A1 region, is substantiallynot parallel to the corresponding region of the surface of the activelayer, e.g. A2 region. The plurality of the ordered pattern units isdisposed in a fixed period, variable period, or quasi-period. The topviews of the plurality of pattern units comprise a polygon, or at leastone pattern selected from the group consisting of triangle, rectangle,hexagon, and circle. The cross-sections of the plurality of patternunits comprise at least one pattern selected from the group consistingof V-shape, semicircle, arc, and polygon. Each of the plurality ofpattern units has a width and a depth, and the depth is preferable lessthan the width for facilitating the subsequently grown buffer layer 102and/or the undoped semiconductor layer 103 to fill into the depressedregion of the patterned surface 101 a.

FIG. 2 shows a light-emitting device 200 in accordance with a secondembodiment of the present disclosure. In comparison with thelight-emitting device 100 shown in FIG. 1, the cross-section of thepatterned surface 101 b comprises a plurality of ordered patternedunits, and each of the patterned units comprises a smooth curve forfacilitating the subsequently grown buffer layer 102 and/or the undopedsemiconductor layer 103 to fill into the depressed area of the patternedsurface 101 b. The method for forming the cross-section with a smoothcurve comprises firstly forming a mask layer of photoresist on a planesubstrate, patterning the mask layer by lithographic process, thencuring the patterned mask layer in a baking machine under an appropriatetemperature to reflow the patterned mask layer of photoresist to form aprofile with smooth curve, finally dry-etching or wet-etching thesubstrate with the patterned mask layer to transfer the smooth curveprofile to the substrate to form a patterned surface 101 b with a smoothcurve as shown in FIG. 2. The top views of the plurality of patternunits comprise polygon, or at least one pattern selected from the groupconsisting of triangle, rectangle, hexagon, and circle.

FIGS. 3A and 3B show a light-emitting device 300 in accordance with athird embodiment of the present disclosure. In comparison with thelight-emitting device 200 shown in FIG. 2, the patterned surface 101 cof the light-emitting device 300 comprises a plurality of patternedunits with variable dimensions or variable patterns disposed in a fixedperiod, variable period, or quasi-period. The top views of the pluralityof the patterned units comprise polygon, or at least one patternselected from the group consisting of triangle, rectangle, hexagon, andcircle. In this embodiment, FIG. 3A shows the cross-section of theplurality of patterned units comprises at least two curves withdifferent curvatures. FIG. 3B shows the patterned units have circularshapes with different diameters or different areas in the top view.

FIG. 4 shows a light-emitting device 400 in accordance with a fourthembodiment of the present disclosure. In comparison with thelight-emitting device 200 shown in FIG. 2, the second contact layer 108of the light-emitting device 400 further comprises an exterior surface108 a having the patterned surface as disclosed in the foregoingembodiments for further enhancing the light extraction efficiency, andany region of the patterned surface 108 a is substantially not parallelto the corresponding region of the upper surface 106 a of the activelayer. The method for forming the exterior surface 108 a of the secondcontact layer 108 comprises naturally growing the second contact layer108 with hexagonal depressions by adjusting the epitaxial growthparameters, such as lowering the growth temperature, or changing the gasconcentration ratio of Hydrogen to Nitrogen, or performing a traditionallithographic and etching process to form the patterned surface 108 awith protrusions and/or depressions. The subsequently formed currentspreading layer 109 is conformable with the patterned surface 108 a andforms a good ohmic contact with the second contact layer 108.

FIG. 5 shows a light-emitting device 500 in accordance with a fifthembodiment of the present disclosure. In comparison with thelight-emitting device 200 shown in FIG. 2, the intermediate layer 502 ofthe light-emitting device 500 comprises a bonding layer, e.g. atransparent adhesive layer or a transparent conductive layer. The firstcontact layer 104 is joined to the second substrate 501 by a bondingtechnique, e.g. a direct bonding method or a thermo-compression bondingmethod. According to the present disclosure, the second substrate 501 isnot limited to a material for epitaxial growth, and is flexible as longas the material meets the purpose, e.g. a material with highconductivity, a material with high transparency, a conductive material,or a material with high reflectivity.

FIG. 6A to FIG. 6D shows the top views of the patterned surface inaccordance with the present disclosure. As shown in FIG. 6A, thepatterned surface comprises a plurality of hexagonal pattern units. Eachof the pattern units is composed of six inclined surfaces 601 adepressed or protruded from the substrate. The six inclined surfaces 601a are commonly joined at a vertex 601 c, and mutually joined at sixconnecting sides 601 b such that the patterned surface of the substrateis substantially not parallel to the corresponding region of the uppersurface 106 a of the active layer. As shown in FIG. 6B, the patternedsurface comprises a plurality of triangular pattern units. Each of thepattern units is composed of three inclined surfaces 602 a depressed orprotruded from the substrate. The three inclined surfaces 602 a arecommonly joined at a vertex 602 c, and mutually joined at threeconnecting sides 602 b such that the patterned surface of the substrateis substantially not parallel to the corresponding region of the uppersurface 106 a of the active layer. As shown in FIG. 6C, the patternedsurface comprises a plurality of rhombus pattern units. Each of thepattern units is composed of four inclined surfaces 603 a depressed orprotruded from the substrate. The four inclined surfaces 603 a arecommonly joined at a vertex 603 c, and mutually joined at fourconnecting sides 603 b such that the patterned surface of the substrateis substantially not parallel to the corresponding region of the uppersurface 106 a of the active layer. As shown in FIG. 6D, the patternedsurface comprises a plurality of square pattern units defined byoverlapped circles. Each of the pattern units is composed of fourinclined surfaces 604 a protruded from the substrate and a rounded topsurface 604 c. The plurality of pattern units are mutually joined at theconnecting sides 604 b such that the patterned surface of the substrateis substantially not parallel to the corresponding region of the uppersurface 106 a of the active layer. The statement of “the patternedsurface of the substrate is substantially not parallel to thecorresponding region of the upper surface of the active layer” asdescribed in the foregoing embodiments does not exclude thecircumstances caused by the various process deviations, such as thephotoresist pattern distortion by lithographic deviation or patterndistortion by etching deviation such that portion of the to-be-patternedsurface is not patterned or portion of the patterned region stillcomprises surface parallel to the active layer. For example, thevertices 601 c, 602 c, 603 c, or rounded top surface 604 c stillpossibly comprises a small mesa under the various process deviations,but the process deviations are preferred to be controlled to have thetotal surface area that is parallel to the active layer and the totalsurface area of the unpatterned surface do not exceed 3% of the totalsubstrate area. As shown in FIG. 6E, the patterned surface comprises aplurality of circular pattern units. Each of the pattern units isdisposed side by side in a tightest disposition such that the patternedsurface area of the substrate that is parallel to the correspondingregion of the upper surface 106 a of the active layer is about 9.3% ornot over 10% of the total substrate area, i.e. the ratio of the area ofthe triangular area subtracting the area of the three sectors to thearea of the triangular area is about 9.3% or not over 10%.

The pattern units as disclosed in the foregoing embodiments have arelative higher patterned proportion, therefore increase the difficultyto epitaxially grow the subsequently buffer layer and the undopedsemiconductor layer. In order to fulfill both light extractionefficiency and internal quantum efficiency, the cross-section of each ofthe pattern units has a width and a depth smaller than the width, i.e.the ratio of the depth to the width is lower than 1, therefore a patternunit with a lower aspect ratio is achieved. The subsequently epitaxiallygrown buffer layer and/or the undpoded semiconductor layer are easilyfilled into the depressed region of the patterned surface to enhance theepitaxial growth quality.

The patterned surface described in the above-mentioned embodiments isnot limited to be formed on any surface of any specific structure of thelight-emitting device in accordance with the present disclosure. It isstill under the scope of the disclosure to form the patterned surface onany structure of the light-emitting device in accordance with thepresent disclosure. For example, the patterned surface can be formed onthe light output surface of the light-emitting device contacting withthe surroundings. The neighboring materials neighbored to the patternedstructure includes but not limited to any structure of thelight-emitting device, the encapsulating material, or the environmentalmedium having a different refraction index from the patterned structure.The difference of the refraction indexes of the patterned structure andthe neighboring material is at least 0.1.

The materials of the buffer layer, the undoped semiconductor layer, thefirst contact layer, the first cladding layer, the second claddinglayer, the second contact layer, and the active layer comprise III-Vcompound materials, e.g. Al_(p)Ga_(q)In_((1-p-q))P orAl_(x)In_(y)Ga_((1-x-y))N, wherein, 0≦p, q, x, y≦1; (p+q)≦1; (x+y)≦1.The first conductivity-type comprises n-type or p-type. The secondconductivity-type comprises n-type or p-type and is different to thefirst conductivity-type. The current spreading layer comprises metaloxide, e.g. ITO, or well-conductive semiconductor layer of phosphide ornitride having high impurity concentration. The growth substratecomprises at least one material selected from the group consisting ofGaP, sapphire, SiC, GaN, and AlN. The second substrate comprises atransparent material selected from the group consisting of GaP,sapphire, Sic, GaN, and AlN, or a heat dissipating material selectedfrom the group consisting of diamond, diamond-like-carbon (DLC), ZnO,Au, Ag, Al, and other metals.

It will be apparent to those having ordinary skill in the art thatvarious modifications and variations can be made to the methods inaccordance with the present disclosure without departing from the scopeor spirit of the disclosure. In view of the foregoing, it is intendedthat the present disclosure cover modifications and variations of thisdisclosure provided they fall within the scope of the following claimsand their equivalents.

What is claimed is:
 1. A light-emitting device comprising: a substratehaving a top surface and a plurality of patterned units protruding fromthe top surface of the substrate; and a light-emitting stack formed onthe substrate and having an active layer with a first surfacesubstantially parallel to the top surface of the substrate, wherein oneof the plurality of patterned units comprises a plurality of connectingsides constituting a polygon shape in a top view of the light-emittingdevice, wherein the one of the plurality of patterned units comprises avertex and a plurality of inclined surfaces respectively extending fromthe plurality of connecting sides, the plurality of inclined surfacescommonly join at the vertex in a cross-sectional view of thelight-emitting device, the vertex being between the top surface of thesubstrate and the first surface of the active layer, and wherein six ofthe plurality of patterned units forms a hexagon in the top view of thelight-emitting device.
 2. The light-emitting device according to claim1, wherein the plurality of inclined surfaces is substantially notparallel to the first surface of the active layer.
 3. The light-emittingdevice according to claim 1, the one of the plurality of patterned unitscomprises a triangular shape in a cross-sectional view of thelight-emitting device.
 4. The light-emitting device according to claim1, wherein the one of the plurality of patterned units comprises a widthand a depth smaller than the width.
 5. The light-emitting deviceaccording to claim 1, wherein the one of the plurality of patternedunits contacts with another one of the plurality of patterned units. 6.The light-emitting device according to claim 1, wherein the polygonshape comprises a triangle, a rectangle, or a hexagon.
 7. Alight-emitting device comprising: a substrate having a top surface and aplurality of patterned units protruding from the top surface; and alight-emitting stack formed on the substrate and having an active layerwith a first surface substantially parallel to the top surface of thesubstrate, wherein one of the plurality of patterned units comprises aplurality of connecting sides constituting a polygon shape in a top viewof the light-emitting device, wherein the one of the plurality ofpatterned units comprises a vertex and a plurality of inclined surfacesrespectively extending from the plurality of connecting sides, theplurality of inclined surfaces commonly joining at the vertex and theplurality of inclined surfaces comprising a triangular shape, andwherein multiple of the plurality of patterned units form a polygonsurrounding another one of the plurality of patterned units in the topview of the light-emitting device.
 8. The light-emitting deviceaccording to claim 7, wherein the plurality of inclined surfaces issubstantially not parallel to the first surface of the active layer. 9.The light-emitting device according to claim 7, wherein the one of theplurality of patterned units comprises a triangular shape in across-sectional view of the light-emitting device.
 10. Thelight-emitting device according to claim 7, wherein the plurality ofpatterned units is periodically arranged on the substrate.
 11. Thelight-emitting device according to claim 7, further comprising anundoped semiconductor layer formed on the substrate and enclosing theplurality of patterned units.
 12. The light-emitting device according toclaim 7, wherein one of the plurality of patterned units comprises awidth and a depth smaller than the width.
 13. The light-emitting deviceaccording to claim 7, wherein the substrate comprises a non-patternedarea parallel to the first surface and the non-patterned area is notgreater than 10% of a total area of the substrate.
 14. Thelight-emitting device according to claim 7, further comprising aneighboring material with a refraction index different from that of thesubstrate.
 15. The light-emitting device according to claim 7, whereinthe one of the plurality of patterned units contacts with another one ofthe plurality of patterned units.
 16. The light-emitting deviceaccording to claim 7, wherein the polygon shape comprises a triangle, arectangle, or a hexagon.
 17. The light-emitting device according toclaim 7, wherein the plurality of patterned units comprises at least twocurves with different curvatures from a cross-sectional view of thelight-emitting device.
 18. A light-emitting device comprising: asubstrate having a top surface and a plurality of patterned unitsprotruding from the top surface; and a light-emitting stack formed onthe substrate and having an active layer with a first surfacesubstantially parallel to the top surface of the substrate, wherein oneof the plurality of patterned units comprises a first inclined line anda second inclined line protruding from the top surface of the substrate,the first inclined line and the second inclined line forming a vertex ina cross-sectional view of the light-emitting device, the one of theplurality of patterned units comprises a non-polygon shape in a top viewof the light-emitting device, wherein three of the plurality ofpatterned units forms a triangle in the top view of the light-emittingdevice.
 19. The light-emitting device according to claim 18, wherein theone of the plurality of patterned units comprises two curves withdifferent curvatures in the cross-sectional view of the light-emittingdevice.
 20. The light-emitting device according to claim 18, theplurality of patterned units comprises a circular shape in a top view ofthe light-emitting device.